Instrument lighting system with inward illumination of the display and outward illumination of nomenclature and index marks

ABSTRACT

An illuminating system for an instrument having a display formed of a plurality of rotatable indicator wheels includes a glass wedge and lamps mounted in the wedge provide rearward illumination of the wheel display through internal reflection of the light in the wedge. A metallic shield having suitable openings to permit display of the illuminated counter wheels is positioned in front of the wedge to minimize glare by blocking at least part of the light projected in the forward direction. In addition, the shield is so configured that a portion of the normally useless forwardly projected light is utilized to illuminate certain indices on the plate such as decimal points and the like. To this end, nomenclature marks such as those identifying the parameter being measured, or index marks such as decimal points, hyphens, etc. are punched through the light shield and suitable diffusers/filters are positioned between the light wedge and these openings to permit illumination of the desired nomenclature and/or index marks by light projected in the forward direction. In this fashion, these elements are illuminated at varying degrees of intensity and/or color by light rays which normally represents lost or stray light, while at the same time, minimizing glare by blocking or elimination the bulk of the stray light from being projected outwardly toward the viewer.

United States Patent [1 1 Thurlow et al.

[ INSTRUMENT LIGHTING SYSTEM WITH INWARD ILLUMINATION OF THE DISPLAY ANDOUTWARD ILLUMINATION OF NOMENCLATURE AND INDEX MARKS UN lTED STATESPATENTS 3,263,646 8/1966 Arnold et al. ..24()/8.l6 X 3,029,334 4/1962Anderson et al. ..24()/l EL 2,907,869 I()/ l 959 Hudson et al ..24(l/lEl.

Primary ExaminerSamuel 5. Matthews Assistant Examiner-Richard A.Wintercorn Attorne vl. David Blumet'eld [4 1 Apr. 24, 1973 [57] ABSTRACTAn illuminating system for an instrument having a display formed of aplurality of rotatable indicator wheels includes a glass wedge and lampsmounted in the wedge provide rearward illumination of the wheel displaythrough internal reflection of the light in the wedge. A metallic shieldhaving suitable openings to permit display of the illuminated counterwheels is positioned in front of the wedge to minimize glare by blockingat least part of the light projected in the forward direction. lnaddition, the shield is so configured that a portion of the normallyuseless forwardly projected light is utilized to illuminate certainindiccs on the plate such as decimal points and the like. To this end,nomenclature marks such as those identifying the parameter beingmeasured, or index marks such as decimal points, hyphens, etc. arepunched through the light shield and suitable diffusers/filters arepositioned between the light wedge and these openings to permitillumination of the desired nomenclature and/or index marks by lightprojected in the forward direction. In this fashion, these elements areilluminated at varying degrees of intensity and/or color by light rayswhich normally represents lost or stray light, while at the same time,minimizing glare by blocking or elimination the bulk of the stray lightfrom being projected outwardly toward the viewer.

9 Claims, 4 Drawing Figures Patented April 24, 1973 INVENTORS WALLACE W.THURLOW LOUIS 3. TRAPASSO BY ATTO INSTRUMENT LIGHTING SYSTEM WITH INWARDILLUMINATION OF THE DISPLAY AND OUTWARD ILLUMINATION F NOMENCLATURE ANDINDEX MARKS This invention relates to an instrument lighting system, andmore particularly, to a wedge lighting system in which glare isminimized due to forwardly projected light while making use of a portionof this normally stray light to illuminate certain instrument markings.I

Wedge lighting systems for illuminating instrument displays are wellknown in the art and incorporate a transparent wedge shaped body whichis positioned in front of a display such as an aircraft instrument dialeither of the pointer or of the wheel counter type. A light source ispositioned above or in the wide or thick portion of the wedge and'thewedges are so configured that multiple internal reflections of the lightcause it to emerge from the interior or rear face of the wedge toilluminate the instrument display.

A certain fraction of the light, however, in undergoing the multipleinternal reflections, emerges from the front face of the wedge in adirection away from the instrument display. This fraction of the lightnot only represents a light loss in that it does not illuminate thedisplay and thus serves no useful purpose, but actually causes glarewhich is highly annoying to the observer, particularly where a greatnumber of such instruments may be mounted in a small space as is oftenthe case in the cockpit of an aircraft. Hitherto, it has been proposedto eliminate the glare, at least partially, by utilizing a second wedgepositioned adjacent to the first wedge with the apex of the second wedgebeing placed adjacent to the base of the first wedge. Thus, light whichemerges from the first wedge in the forward direction strikes the secondwedge and because of refraction will undergo multiple internalreflections in the second wedge and is either trapped or utilized toilluminate another display. Typical of such prior art approaches are thesystems described and shown in US. Pat. No. 3,040,168, 2,646,637,2,761,056 and the like.

It will be obvious, however, that the double wedge configurations forilluminating a display while effective in reducing glare, requires theuse of an additional wedge which represents additional cost, weight andspace, as well as additional complexityin manufacturing and assembly.Consequently, a need exists for an illumination system for an instrumentwhich eliminates or minimizes glare, while yet avoiding the need foradditional wedge elements which add costs and complexity to the device.Furthermore, it would also be highly desirable to provide a wedgeilluminating system in which the glare is substantially eliminated,while at the same time, selectively using portions of the forwardprojected light for useful purposes. To this end, applicant hasdeveloped a system in which the forwardly projected light from a singlewedge is blocked by a suitable shielding means to eliminate asubstantial amount of glare, while at the same time, selected portionsof the forwardly projected light are utilized to illuminate nomenclaturemarkings and indices on the instrument face or shield with theillumination to the nomenclature and indices being controlled inintensity and color by means of suitable filters and diffusers.

It is therefore, a principal objective of the instant invention toprovide a wedge lighting illumination system in which glare is minimizedand the normally undesirable forwardly projected light is selectivelyutilized to illuminate nomenclature and index markings.

Another objective of the invention is to provide an instrumentillumination system of the wedge type whichminimizes glare and providesselective illumination of nomenclature and indices which is light inweight, low in cost and easy to manufacture.

- Other objectives and advantages of the instant invention will becomeapparent as the description thereof proceeds.

In carrying out the invention and realizing the various objectives, aninstrument illumination system is provided in which a single wedgelighting element is positioned adjacent to a counter wheel display of aninstrument. A plurality of lamps are positioned within the thick portionof the wedge with the light from the lamps being reflected internally sothat light is emitted inwardly to illuminate the display. Positioned onthe other side of the wedge is a suitable shield member which contains aplurality of openings to permit display of the numbers or indicatingmarks on the counter wheel. The shield is also provided with selectednomenclature and index marks in the form of openings in the shield.Light from the wedge is emitted in the forward direction projectsthrough these openings. One or more filter and. diffusing means whichcontrol the intensity and/or color of the illumination field arepositioned between the nomenclature and index openings and the wedge. Inthis manner, a substantial portion of the forwardly projected light,which normally constitutes objectionable glare, is blocked by theshield, while selected portions thereof are permitted to pass throughthe nomenclature and index openings to provide illumination of thesemarks and thereby serve a useful function.

The novel features which are believed to be characteristic of thisinvention are set forth with particularity in the appended claims. Theinvention itself, however, as to its organization and method ofoperation, may be best understood by reference to the followingdescription taken in connection with the accompanying drawings in which:

FIG. 1 is an exploded, perspective view of the illuminating system andthe display wheel counters constituting the display;

FIG. 2 is an elevational view of the instrument;

FIG. 3 is a partially broken away section taken along the lines 3-3 ofFIG. 2;

FIG. 4 is a schematic diagram of a lighting wedge i1 lustrating thelight ray paths.

FIG. 1 shows an exploded, perspective view of a wedge lightingarrangement 1 positioned in front of an instrument display which in thisinstance, includes a plurality of rotatable counter wheels 2. Thecounter wheels are actuated by any suitable mechanism such aselectromagnetic actuators, for example, in response to the parameter tobe measured. The instrument lighting system includes a lightdistributing glass wedge 4 positioned directly in front of the wheelcounters. A plurality of light sources such as the bulbs 5, arepositioned at the base or thick portion of the wedge. The bulbs, whichmay be energized in any suitable manner, are shown mounted in openings 6in the base of the wedge although other mounting arrangements for thebulbs are equally feasible. The light from the bulbs enters the wedge 4and by means of multiple internal reflections the major portion of thelight emerges from the rear face of the wedge and provides rearwardillumination of counter wheels.

Positioned in front of the glass wedge is an arrangement for controllingtransmission of the light energizing from the front face of wedge 4 tominimize glare and for utilizing a portion of this light to illuminatecertain markings and indices on the instrument face. To this end, ametallic shield 7 is provided which contains a plurality of openings 8for permitting display of the counter wheels. In addition to a number oflight transmitting, nomenclature or index markings are provided in theform of openings extend entirely through the shield. Thus, for example,suitable nomenclature mark describing the parameter being measured, suchas the designation EPR (representing engine pressure ratio), indicatedgenerally at 9, is punched or stamped or otherwise extends through theshield. Similarly, indices such as decimal points 10 or an interpolationmark such as the dash lll project through the shield so that forwardlyprojected light from the wedge passes through and illuminates theseopenings. In this fashion, a portion of the normally useless forwardlyemitted light serves a useful purpose.

Positioned between the shield and the glass wedge are a plurality offilter/diffuser elementsl2 which are selectively positioned betweenwedge 4 and the nomenclature or index openings 9, 10 and 11. In FIG. thefilter/diffuser elements 12 are shown schematically. It will beunderstood that these are of the proper configuration and are suitablypositioned to overlie the nomenclature and index openings at 9, l0 and11. The filter/diffuser elements are suitably fastened to the back ofthe shield plate 7 by any commercially available adhesive and cover theopenings so that the forwardly emitted light from wedge 4 is transmittedthrough these elements to control both in the intensity of theillumination of these openings as well as the color, if that is desired.Thus, these filter/diffuser elements may, in a preferred embodiment,[where only simple illumination of the nomenclature, index. orinterpolation marks is desired] constitute transparent plastic membershaving white paint sprayed thereon. The density and amount of paint onthe surface of the device will obviously control the intensity of thetransmitted light. In addition to controlling the intensity of theforward illumination and hence, the brightness of the marks and indices,the elements 12' may be of the type to produce selective spectralillumination of these openings. Thus, if a red filter element isutilized, thereby passing only light in the red portion of the spectrum,the marks will be illuminated by red light. Similarly, other filters maybe used to provide any desired color.

The entire lighting assembly, wedges, shield, etc. is fastened bysuitable fastening means through openings 13 and 14 in the shield andwedge member 4 to the instrument housing, not shown.

FIGS. 2 and 3 illustrate the instrument wedge lighting arrangement ofthe invention mounted in an instrument housing. The wedge lightingsystem is mounted in instrument housing and is secured to face plate 21and the housing by a plurality of fastening means such as the screws 22which pass through mounting holes 23 in the face plate. These mountingholes align with mounting holes 13 and 14 in shield 7, and light wedge 4respectively. The screws 22 are fastened to a rib or mounting flange 25(which may be seen most clearly in FIG. 3) in the interior of thehousing thereby firmly securing the entire assembly in the instrumenthousing.

Face plate 21 has an opening 26 through which the shield member 7 andthe counter wheels 2 are visible. The opening is sufficiently large toexpose display openings 8 in shield 7 as well as the nomenclature marks,namely the letters EPR representing engine pressure ratio, the decimalpoints 10 and the interpolation mark 11 to view. These marks 9, l0 and11, as pointed out previously, are illuminated by a portion of theforward projected light from the lighting system while the remainingforwardly projected light is blocked by shield 7. Also, positionedwithin the opening 26 of the shield is a pane of transparent material 28which may be either glass or the like which covers and protects shield7. The bulbs which constitute the source of illumination for the wedgelighting system are, as shown in FIG. 3, positioned in openings 6 inglass wedge 4. Counter wheels 2 which constitute the display of theinstrument are positioned directly behind the wedge so that majorportion of the light from bulbs is internally reflected and emerges fromthe rear of the wedge to illuminate the counter wheels.

FIG. 4 illustrates schematically the light distribution within the wedgeand the manner in which the shield 7 blocks a portion of the forwardlyprojected light from the wedge to block the major part of this light tominimize glare while selectively utilizing a portion of this forwardlyprojected light to illuminate nomenclature, index or interpolation markin the shield. FIG. 4 is highly exaggerated in size and idealized inform in order to illustrate the principles rather than the actualconstructional details. For one thing, the filter/diffuser elements 12shown in FIG. 1 have, for the sake of simplicity of illustration, notbeen illustrated in FIG. 4. Only the wedge and the shield and theopenings 9, 10 and ll, the size of which has been exaggerated foremphasis, are shown in FIG. 4. Furthermore, the light source such as thebulbs 6 which project to the openings 5 in the wedge has not been shownin order to simplify the drawing. Thus, a single point source of light30, which represents the plurality of light sources which are actuallyrepresented by the bulb is shown at the surface of wedge opening 5. Thelight rays 31 enter the wedge and are initially totally reflected fromthe opposing surfaces of the wedge since they strike the surfaces at anangle which is greater than the critical angle of total reflection. As aresult, multiple total reflections from the inner surfaces occur. Afterthe initial reflections, the light rays will eventually achieve an anglewith respect to these surfaces which are less than the critical angle oftotal reflection and more and more of the light rays emerge as shown at32 in the rearward direction to illuminate the counter wheels. However,not all of the rays are totally reflected at the interior surface and anumber of these indicated by the dashed lines 33 emit from the forwardsurface of the wedge and therefore, represent forward illumination whichnormally represents glare from the instrument face.

However, due to the presence of the shield 7, substantial portions ofthis forward illumination is blocked by the shield and prevented frombeing emitted into the cockpit as a form of the glare. Selected lightrays shown generally by the dashed lines 34 however, are projectedthrough openings 9, and 11 representing index, interpolation andnomenclature marks and serve to illuminate these marks. In this manner,a portion of the forwardly projected light which is normally present asundesirable glare performs a useful function in illuminating the variousmarks or indices on the instrument plate. The remaining forwardlyprojected light is effectively blocked by the shield thereforeminimizing the glare from the instrument case.

It will be appreciated from FIG. 4 that the light ray 7 distributionshows highly simplistic version of what occurs. Only a single reflectionof the light is shown for simplicity of illustration. It will be furtherunderstood that a multiplicity of such internal reflections take placebefore the light rays impinging on the sides of the tion of both theforward and rearward emitter light and the manner in which the forwardemitted light is blocked by the shield and only a selected portionthereof passes through the openings in the shield to illuminate theindices, nomenclatures etc.

It can be seen from the foregoing description that a simple andeffective wedge lighting assembly has been provided in which forwardlyemitted light from the lighting system is blocked except for theselected portions thereof that are utilized to illuminate the variousmarks on the instrument face. In this manner, glare is minimized,illumination of indices and other marks is provided, while at the sametime, providing a simple arrangement in which this is achieved withoutthe use of other matching and expensive wedge elements for a lightdistribution arrangement.

Although one particular embodiment of the invention has been shown anddescribed above, it will, of course, be understood that the invention isnot limited thereto since many modifications in the structure andarrangement may be made. It is contemplated by the appended claims, anysuch modifications asforwarded in the true spirit and scope of thisinvention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States:

1. In a lighting system for illuminating an instrument display thecombination comprising a. an instrument display, b. a transparent wedgeshaped body positioned in front of said display for illuminating saiddisplay by light emitted rearwardly from said wedge after multipleinternal reflections,

c. a light source so positioned with respect to the thick portion of thewedge for introducing light into the wedge,

. means for controlling transmission of light emitted frontwardly fromsaid wedge to minimize glare and utilize selected portions thereof toilluminate selected marking on the instrument face, including e.shielding means positioned in front of said wedge to bloc k forwardly eitted light from said weduge, said shielding means including meansdefining isplay openings extending therethrough and aligned with saiddisplay, and further opening means extending through said shieldrepresenting index or nomenclature marks so that a portion of the for-'wardly emitted light is transmitted through said further openings toilluminate said marks with forwardly emitted light.

f. .At least one light transmission control element positioned betweenthe wedge and said further openings to control the characteristics ofthe light transmitted through the further openings and the illuminationof the marks represented thereby.

2. The lighting system according to claim 1 wherein said display meanscomprises a plurality of counter wheels and said display openingincludes a plurality of openings aligned with said plurality of wheels.

3. The lighting system according to claim 1 wherein said wedge includesopening means extending through the thick portion of the wedge and saidlight source is positioned in the opening in the wedge.

4. The lighting system according to claim 1 in which the lighttransmission control element controls the intensity of the lighttransmitted through the further openings.

5. The lighting system according to claim 1 in which the lighttransmission control element controls the spectral characteristic of thelight transmitted through the further openings.

6. The lighting system according to claim 1 in which the lighttransmission control element controls both the intensity and spectralcharacteristic of the light transmitted through the further openings.

7. The lighting system according to claim 2 including lighttransmission'control elements positioned between the wedge and saidfurther openings to control the characteristics of the light transmittedtherethrough.

8. The lighting system according to claim 7 wherein said furtheropenings represent nomenclature marks identifying the parameter beingmeasured. 1

9. The lighting system according to claim 8 wherein said furtheropenings also include further indeces.

1. In a lighting system for illuminating an instrument display thecombination comprising a. an instrument display, b. a transparent wedgeshaped body positioned in front of said display for illuminating saiddisplay by light emitted rearwardly from said wedge after multipleinternal reflections, c. a light source so positioned with respect tothe thick portion of the wedge for introducing light into the wedge, d.means for controlling transmission of light emitted frontwardly fromsaid wedge to minimize glare and utilize selected portions thereof toilluminate selected marking on the instrument face, including e.shielding means positioned in front of said wedge to block forwardlyemitted light from said wedge, said shielding means including meansdefining display openings extending therethrough and aligned with saiddisplay, and further opening means extending through said shieldrepresenting index or nomenclature marks so that a portion of theforwardly emitted light is transmitted through said further openings toilluminate said marks with forwardly emitted light. f. At least onelight transmission control element positioned between the wedge and saidfurther openings to control the characteristics of the light transmittedthrough the further openings and the illumination of the marksrepresented thereby.
 2. The lighting system according to claim 1 whereinsaid display means comprises a plurality of counter wheels and saiddisplay opening includes a plurality of openings aligned with saidplurality of wheels.
 3. The lighting system according to claim 1 whereinsaid wedge includes opening means extending through the thick portion ofthe wedge and said light source is positioned in the opening in thewedge.
 4. The lighting system according to claim 1 in which the lighttransmission control element controls the intensity of the lighttransmitted through the further openings.
 5. The lighting systemaccording to claim 1 in which the light transmission controL elementcontrols the spectral characteristic of the light transmitted throughthe further openings.
 6. The lighting system according to claim 1 inwhich the light transmission control element controls both the intensityand spectral characteristic of the light transmitted through the furtheropenings.
 7. The lighting system according to claim 2 including lighttransmission control elements positioned between the wedge and saidfurther openings to control the characteristics of the light transmittedtherethrough.
 8. The lighting system according to claim 7 wherein saidfurther openings represent nomenclature marks identifying the parameterbeing measured.
 9. The lighting system according to claim 8 wherein saidfurther openings also include further indeces.